We have reported in the past about visits from some robots recording in your Analytics statistics reports and biasing your sessions and referrals data.
We are seeing more and more of these escaping Google’s methods to try to exclude them. For one client these amounted to 30% of their traffic!
If you are seeing lots of sessions from Brazil it is probably visits from semalt.com and not real visitors
Other robots and stats hijack sites that we have noted include;
Filters can be set up to remove these from your stats. Contact us for help on this if need be.